A typical vehicle air bag system comprises an inflator or gas generator, an air bag, and a container enclosing the inflator and the air bag. The air bag, while in the container, is folded into a predetermined configuration. Upon actuation of the inflator, gas at relatively high pressure is directed into the air bag. The bag is deployed through a portion of the container and is inflated to a predetermined configuration. In that predetermined configuration, the air bag is designed to restrain a vehicle occupant against impacting a portion of the vehicle.
Because space requirements are increasingly important in vehicle design, it is important that an air bag be capable of being folded into a relatively compact package size, so that it can be disposed in a container of relatively small size. Also, as the number of air bags being installed in vehicles increases, it becomes increasingly important to provide efficient and effective ways of mass producing air bags.
A known structure for a vehicle air bag comprises several pieces of fabric cut into different shapes (e.g., rectangular, circular, etc.), and fastened together, preferably sewn together, to form the air bag. An opening formed in one of the pieces of fabric functions as a gas inlet opening for the air bag. Often, some additional fabric is attached to the air bag in proximity to the gas inlet opening. The additional fabric is useful in supporting retaining means, such as rigid metal bars, which enables the air bag to be securely attached to a portion of the container.
Forming an air bag by securing together pieces of fabric has certain drawbacks. Substantial manufacturing time is required to cut the fabric into different configurations, to orient the pieces of fabric properly relative to each other, and to sew the pieces of fabric to each other while in the proper orientation. Also, because the fabric is cut into different geometric shapes, which are not all rectangular, certain amounts of fabric are lost as the non-rectangular pieces are cut. Such drawbacks are particularly significant considerations in respect to mass production of air bags.
In the patent literature, there have been some suggestions for air bag structures in which the air bag is formed by a single piece of material, which forms a three-dimensional configuration when the air bag is inflated. For example, U.S. Pat. No. 4,010,055, discloses a single piece of fabric material formed into an open tube. The tube is flattened to a rectangular shape and then sealed along its open ends. An opening is formed in the flattened tube to serve as a gas inlet opening. To complete the air bag, the flattened tube is folded and sewn to form additional seams to obtain the desired predetermined air bag configuration.
U.S. Pat. No. 4,006,918 discloses a dual chambered air bag formed from a single piece of fabric material. The air bag has an opening for receiving an inflator. To form the air bag, the material is first folded upon itself and stitched along portions of the open sides and ends. The bag is then folded again, turned inside-out, and sewn along open sides to form an inner chamber and an outer chamber. The inflator is inserted through the opening and positioned so that it is in fluid communication with each of the inner and outer chambers.
U.S. Pat. No. 3,910,654 also discloses an air bag having a predetermined three-dimensional configuration formed from a single piece of fabric material. To form the air bag, the material is first folded upon itself and stitched along its open sides. Material surrounding an open end is again folded and stitched to form a double layer of material surrounding the open end. The bag is then turned inside-out, folded, and stitched to form the three-dimensional configuration.
The air bag disclosed in each of the foregoing patents has a relatively complex three-dimensional configuration having side walls intermediate two layers of material, and requiring numerous folds and sewn seams to manufacture the air bag. The air bag disclosed in each of U.S. Pat. Nos. 4,006,918 and 3,810,654 also require the air bag to be turned inside-out between folding and sewing steps.
Applicants believe there is a continuing need to simplify the structure and techniques for forming air bags, especially in view of the need to produce the air bags by mass assembly techniques.